1. Field of the Invention
This invention relates to imide-diurea and imide-urethane urea grease thickeners made in situ as a one pot preparation involving a sequential reaction but without making use of any organic solvents.
2. Description of the Related Art
Grease is a semi-fluid medium comprised of a liquid lubricant and a thickener. The liquid lubricant is derived from natural mineral oils, synthetic hydrocarbons, esters, ethers, polysiloxanes, fluorocarbon polymers etc. A wide variety of compounds are used as thickeners. For example mineral oils are thickened by alkali or alkaline earth metal soaps of fatty acids, clays, polymers, phthalocyanines, organic dyes, polyureas and others. The most commonly used thickners are those containing lithium, calcium, or sodium salts of natural fatty acids. At present, lithium soaps of stearic acid and 12-hydroxy stearic acid is commonly used. Imide-urea thickeners have also been used, as disclosed in JP 79 114 506, in which acetone, a volatile organic solvent is used to dissolve the starting materials. U.S. Pat. No. 5,585,335 describes the use of a metal salt based on imide-carboxylic acid in combination with a bi-metal phthalate complexing agent. JP 57 109 896 discloses lubricating greases manufactured by compounds containing 4 to 8 imide groups per molecule, in which the starting materials are dissolved in N,N-dimethyl formamide, a non-volatile, high-boiling organic solvent. JP 56 139 592 discloses lubricating oils thickened by two imide and two amide groups per molecule in which acetone is used as a carrier for the anhydride and the amine. Another Japanese patent publication JP 54 113 605 discloses a lubricating grease thickened with an imide compound, in which acetone is used to dissolve the anhydride and amino compounds.
An object of this invention is to propose a process for the preparation of imide-diurea and imide-urethane urea grease thickeners.
Another object of this invention is to propose a process for the preparation of imide-diurea and imide-urethane urea grease thickeners which avoids the use of volatile or non-volatile, low-boiling or high-boiling organic solvent.
Still another object of this invention is to propose a process for the preparation of imide-diurea and imide-urethane urea grease thickeners which avoids the difference in reactivity of the reactants employed and to maximize the formation of products capable of thickening the oil of lubricating quality.
A further object of this invention is to propose a process for the preparation of imide-diurea and imide-urethane urea grease thickeners which exhibits excellent storage stability without showing any age hardening tendency.
A still further object of this invention is to propose a grease and a grease thickening system.